The invention relates to an assembling type rotor structure of brushless direct-current (DC) motor, and more particularly, to a rotor structure that provides embedded type of assembling, low manufacturing cost, and very firm fixation after being assembled.
The rotor of brushless DC motors in the prior art is usually formed with a permanent magnet 10 and silicon steel sheets 11 as in the referenced R.O.C. Patent 327485 and 412100 shown in FIG. 1 and FIG. 2 respectively. The permanent magnet is covered on the rims of the silicon steel sheets and has to match the curvature of the circular arc of the outer stator of the inner rotor/outer stator brushless DC motor. Similarly, it has to match the shape of the vertex of the inner stator of outer rotor/inner stator brushless DC motor to be tightly fitted.
In general, the silicon steel sheets of the rotor of brushless DC motor in prior art are formed by stacking up a plurality of individual silicon steel sheet of the same size and configuration. There is no problem for manufacturing such silicon steel sheet when the rotor is applied in a small-diameter brushless DC motor. Nevertheless, the cost of manufacturing large-diameter brushless DC motor with stacked silicon steel sheets increases greatly due to the requirement of a heavy duty punching machine with high impact force. Besides, when it comes to punching silicon steel sheets, it is a waste of material for having a lot of remaining material. On the other hand, there exists some techniques to fit and attach the permanent magnet and the silicon steel sheets together, but none of the techniques in prior art provides solutions for the loosening problem of the permanent magnet and for the difficulty in controlling precise dimension. Although improvements have been made for these disadvantages in the R.O.C. Patent 327485 and 412100, as shown in FIG. 1 and FIG. 2 respectively, the manufacturing cost is rather high. This is because that the production of the permanent magnet has the requirement of matching the curvature of the circular arc of the outer stator""s internal surface and the fixed scoop channels on the two sides. What is more, the techniques of the prior art are applicable only in inner rotor/outer stator brushless DC motor, but not easily applicable in outer rotor/inner stator brushless DC motor, therefore, the scope of application is limited.
FIG. 3 and FIG. 4 are the prior arts of U.S. Pat. Nos. 5,929,120 and 5,886,441 respectively. As shown in FIG. 3 and FIG. 4, the silicon steel sheets 12 are formed with disassembled steel sheet units, and having containing slots 13 in the silicon steel sheets for housing the permanent magnets which are in rectangular shape instead of the round shape. The fixation technique to hold the silicon steel sheets and the axis of the rotor structure in place is to employ fixation pins and the rotor""s front and rear caps. The disadvantage of this kind of fixation technique is that the pins are subject to be bent and distorted when the silicon steel sheets so stacked are relatively lengthy.
In light of the above-mentioned disadvantages of the prior art, the invention provides an assembling type rotor structure of brushless DC motor. The rotor structure includes a rotor""s main body having a plurality of ribs and a plurality of embedded small teeth that can be disassembled in axial direction. Each of these small teeth has a scoop channel having configuration and size matching those of the ribs of the rotor""s main body. In this way, the small teeth can be embedded and fitted into the rotor""s main body in axial direction while providing a rather firm fixation. Moreover, the containing slot formed between each pair of the adjacent embedded type small teeth allows the permanent magnet be embedded and fixed therein.
Therefore, one of the objects of the invention is to provide a type of rotor structure of brushless DC motor with embedded design of permanent magnets.
Another object of the invention is to provide a rotor structure that is applicable in both the outer stator/inner rotor and the inner stator/outer rotor brushless DC motor.
Further object of the invention is to provide a rotor structure such that when the assembling type rotor structure is applied in smaller outer diameter motor, the small teeth of axially embedded type can be combined to form an annular silicon steel sheet.
To accomplish the above-mentioned objects, the invention provides an assembling type rotor structure of brushless DC motor. The rotor structure includes a main body having a plurality of ribs made of non-permeable material and a plurality of embedded type small teeth formed by punching and stacking up a plurality of permeable silicon steel sheets. Each of the embedded type small teeth has a scoop channel having configuration and size matching those of the ribs of the rotor""s main body to enable embedding and tightly fitting the small teeth to the rotor""s main body in axial direction. In this way, each small tooth cannot be moved in tangential nor in radial direction on the plane perpendicular to the axis, thereby, providing a rather firm fixation. Moreover, the containing slot formed between each pair of the adjacent embedded type small teeth allows the permanent magnet to be embedded and fixed therein. A rotor structure of brushless DC motor can then be formed by locking up with a front and a rear sealing caps at the front and rear ends of the rotor""s main body to hold the permanent magnets and the embedded type small teeth in place.
In order to understand fully the objects, characteristics, and the efficacy of the invention, a detailed illustration with accompanied drawing is described as follows: